Auer rods are associated with which leukemia and what do they indicate?

• A. AML; presence supports myeloid differentiation.
• B. ALL; indicate lymphoid origin.
• C. CML; indicate basophil proliferation.
• D. Hairy cell leukemia; indicate hairy cell.

Answer: (A)

Auer rods signal myeloid differentiation and point to acute myeloid leukemia. These needle‑like, azurophilic inclusions inside blasts are formed from fused primary granules with myeloperoxidase activity. Their presence in leukemic blasts indicates the cells are of the myeloid lineage, which is characteristic of AML (and is especially noted in subtypes like acute promyelocytic leukemia). They are not features of lymphoid leukemias such as ALL, nor of CML or hairy cell leukemia, whose blasts do not contain Auer rods. So, finding Auer rods supports a diagnosis of AML and confirms myeloid origin of the malignant cells.